Modelagem do fluxo da barragem Eng. Armando Ribeiro Gonçalves (Açu/RN) e análise da eficácia de dispositivos de vedação em fundação permeável

Abstract

This paper aims to understand the behavior of the Engenheiro Armando Ribeiro Gonçalves earth dam by means of numerical seepage modelling. It is located in the basin of Piranhas-Açu River, in the state of Rio Grande do Norte and it was built over a high permeability soil foundation. Such dams are more susceptible to piping and sand liquefaction. In order to avoid damage in those structures it is indispensable the use of sealing devices. The focus of this paper, at a first moment, was the water flow analysis under the stationary state condition using the software SLIDE® version 7.017 from Rocscience. Pore pressure values were compared to those obtained with the three piezometers installed at the dam. The values obtained for two piezometer showed a good agreement with the instrumentation data. The third one showed a value equal to the half of that presented by instrumentation. Afterwords, it was verified the sealing system effectiveness which was used at the dam foundation (full upstream cut off wall), which resulted in an average effectiveness of 75% in relation to the flow parameters (discharge, uplift pressure and outlet gradient). Subsequently, analyses were performed in order to check other possibilities of foundation sealing devices: partial cut off wall, impermeable blanket and diaphragm wall. Among those devices, only the full cut off wall with average effectiveness of 80% and the diaphragm wall with 100% were suitable for sealing the foundation.